Measurement framework for beam failure detection and radio link monitoring

ABSTRACT

According to a first aspect of embodiments herein, the object is achieved by a method performed by a User Equipment (UE) for monitoring a beam transmitted by a base station in a radio communications network. The base station is serving the UE. The UE monitors ( 1202 ) a reference signal related to the beam, from the base station. Each time a quality of the reference signal is below a first threshold, the UE generates ( 1203 ) an Out-Of-Synchronization (OOS) event 
     When the number of OOS events reaches an OOS Beam Failure Detection (BFD) threshold, the UE triggers ( 1205 ) a beam recovery preparation procedure, and
         when the number of OOS events reaches an OOS Radio Link Monitoring (RLM), threshold, the UE starts ( 1206   a ) an RLF timer.

TECHNICAL FIELD

Embodiments herein relate to a User Equipment (UE) a base station andmethods therein. In particular, they relate to for monitoring a beamtransmitted by a base station in a radio communications network and forconfiguring a UE to monitor a beam transmitted the a base station in aradio communications network.

BACKGROUND

In a typical wireless communication network, wireless devices, alsoknown as wireless communication devices, mobile stations, stations (STA)and/or User Equipments (UE), communicate via a Local Area Network suchas a WiFi network or a Radio Access Network (RAN) to one or more corenetworks (CN). The RAN covers a geographical area which is divided intoservice areas or cell areas, which may also be referred to as a beam ora beam group, with each service area or cell area being served by aradio network node such as a radio access node e.g., a Wi-Fi accesspoint or a radio base station (RBS), which in some networks may also bedenoted, for example, a NodeB, eNodeB (eNB), or gNB as denoted in 5G. Aservice area or cell area is a geographical area where radio coverage isprovided by the radio network node. The radio network node communicatesover an air interface operating on radio frequencies with the wirelessdevice within range of the radio network node.

Specifications for the Evolved Packet System (EPS), also called a FourthGeneration (4G) network, have been completed within the 3rd GenerationPartnership Project (3GPP) and this work continues in the coming 3GPPreleases, for example to specify a Fifth Generation (5G) network alsoreferred to as 5G New Radio (NR). The EPS comprises the EvolvedUniversal Terrestrial Radio Access Network (E-UTRAN), also known as theLong Term Evolution (LTE) radio access network, and the Evolved PacketCore (EPC), also known as System Architecture Evolution (SAE) corenetwork. E-UTRAN/LTE is a variant of a 3GPP radio access network whereinthe radio network nodes are directly connected to the EPC core networkrather than to RNCs used in 3G networks. In general, in E-UTRAN/LTE thefunctions of a 3G RNC are distributed between the radio network nodes,e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPShas an essentially “flat” architecture comprising radio network nodesconnected directly to one or more core networks, i.e. they are notconnected to RNCs. To compensate for that, the E-UTRAN specificationdefines a direct interface between the radio network nodes, thisinterface being denoted the X2 interface.

Multi-antenna techniques can significantly increase the data rates andreliability of a wireless communication system. The performance is inparticular improved if both the transmitter and the receiver areequipped with multiple antennas, which results in a Multiple-InputMultiple-Output (MIMO) communication channel. Such systems and/orrelated techniques are commonly referred to as MIMO.

In addition to faster peak Internet connection speeds, 5G planning aimsat higher capacity than current 4G, allowing higher number of mobilebroadband users per area unit, and allowing consumption of higher orunlimited data quantities in gigabyte per month and user. This wouldmake it feasible for a large portion of the population to streamhigh-definition media many hours per day with their mobile devices, whenout of reach of Wi-Fi hotspots. 5G research and development also aims atimproved support of machine to machine communication, also known as theInternet of things, aiming at lower cost, lower battery consumption andlower latency than 4G equipment.

Multi-Antenna Schemes in NR

Multi-antenna schemes for NR are currently being discussed in 3GPP. ForNR, frequency ranges up to 100 GHz are considered. It is known thathigh-frequency radio communication above 6 GHz suffers from significantpath loss and penetration loss. One solution to address this issue is todeploy large-scale antenna arrays to achieve high beamforming gain,which is a reasonable solution due to the small wavelength ofhigh-frequency signal. Therefore MIMO schemes for NR are also calledmassive MIMO. For around 30/70 GHz, up to 256 Transmit (Tx) and Receive(Rx) antenna elements are assumed. Extension to support 1024Tx at 70 GHzis agreed and it is under discussion for 30 GHz. For sub-6 GHzcommunication, to obtain more beamforming and multiplexing gain byincreasing the number of antenna elements is also a trend.

With massive MIMO, three approaches to beamforming have been discussed:analog, digital, and hybrid which is a combination of the two.

The analog beamforming would compensate high pathloss in NR scenarios,while digital precoding would provide additional performance gainssimilar to MIMO for carrier frequencies below 6 GHz, so-called sub-6 GHzscenarios. The implementation complexity of analog beamforming issignificantly less than digital precoding. This is since it relies onsimple phase shifters. However, the drawbacks are its limitation inmulti-direction flexibility, i.e. only a single beam can be formed at atime and the beams are then switched in time domain. Only widebandtransmissions, i.e. not possible to transmit over a subband, unavoidableinaccuracies in the analog domain, etc.

Digital beamforming used today in LTE, requires costly converters toand/or from the digital domain from and/or to IF domain. However, itprovides the best performance in terms of data rate and multiplexingcapabilities wherein multiple beams over multiple subbands at a time canbe formed, but at the same time it is challenging in terms of powerconsumption, integration, and cost; in addition to that the gains do notscale linearly with the number of transmit and/or receive units whilethe cost is growing rapidly.

Supporting hybrid beamforming, to benefit from cost-efficient analogbeamforming and high-capacity digital beamforming, is thereforedesirable for NR. An example diagram for hybrid beamforming is shown inFIG. 1, wherein

IFFT means Inverse Fourier transform,

P/S means parallel to serial conversion,

DAC means Digital Analogue Converter, and

PA means power amplifier.

Beamforming may be on transmission beams and/or reception beams, networkside or UE side.

Beam Sweeping

The analog beam of a subarray may be steered toward a single directionin each OFDM symbol, and hence the number of subarrays determines thenumber of beam directions and the corresponding coverage on each OFDMsymbol. However, the number of beams to cover the whole serving area istypically larger than the number of subarrays, especially when theindividual beam-width is small, also referred to as narrow. Therefore,to cover the whole serving area, multiple transmissions with narrowbeams differently steered in time domain are also likely to be needed.The provision of multiple narrow coverage beams for this purpose hasbeen called “beam sweeping”. For analog and hybrid beamforming, the beamsweeping seems to be essential to provide the basic coverage in NR. Forthis purpose, multiple OFDM symbols, in which differently steered beamscan be transmitted through subarrays, may be assigned and periodicallytransmitted.

FIG. 2 depicts Tx beam sweeping on 2 subarrays.

FIG. 3 depicts Tx beam sweeping on 3 subarrays.

Synchronisation Signal (SS) Block Configuration

Herein a non-limiting example of SS block and SS burst configuration isdescribed which may be assumed in other embodiments.

SS Block:

NR-PSS, NR-SSS and/or NR-PBCH can be transmitted within an SS block. Fora given frequency band, an SS block corresponds to N OFDM symbols basedon a certain e.g. a default subcarrier spacing, and N is a constant. UEshall be able to identify at least OFDM symbol index, slot index in aradio frame and radio frame number from an SS block. A single set ofpossible SS block time locations (e.g., with respect to radio frame orwith respect to SS burst set) is specified per frequency band. At leastfor multi-beams case, at least the time index of SS-block is indicatedto the UE. The position(s) of actual transmitted SS-blocks can beinformed for helping CONNECTED/IDLE mode measurement, for helpingCONNECTED mode UE to receive DL data/control in unused SS-blocks andpotentially for helping IDLE mode UE to receive DL data/control inunused SS-blocks.

SS Burst:

One or multiple SS block(s) compose an SS burst. The maximum number ofSS-blocks, L, within SS burst set may be carrier frequency dependent,e.g.:

-   -   For frequency range category #A (e.g., 0˜6 GHz), the number (L)        is TBD within L≤[16]    -   For frequency range category #B (e.g., 6˜60 GHz), the number is        TBD within L≤[128]

SS Burst Set:

One or multiple SS block(s) compose an SS burst set. The maximum numberof SS-blocks, L, within SS burst set may be carrier frequency dependent,e.g.

-   -   For frequency range category #A (e.g., 0-3 GHz), the number (L)        is L=4    -   For frequency range category #B (e.g., 3-6 GHz), the number (L)        is L=8    -   For frequency range category #A (e.g., 6-60 GHz), the number (L)        is L=64

SS Burst Set Transmission:

From physical layer specification perspective, at least one periodicityof SS burst set is supported. From UE perspective, SS burst settransmission is periodic. At least for initial cell selection, a UE mayassume a default periodicity of SS burst set transmission for a givencarrier frequency, e.g. one of 5 ms, 10 ms, 20 ms, 40 ms, 80 ms, or 160ms. The UE may assume that a given SS block is repeated with a SS burstset periodicity. By default, the UE may neither assume the gNB transmitsthe same number of physical beam(s), nor the same physical beam(s)across different SS-blocks within an SS burst set.

For each carrier, the SS blocks may be time-aligned or overlap fully orat least in part, or the beginning of the SS blocks may be time-aligned,e.g. when the actual number of transmitted SS blocks is different indifferent cells.

FIG. 4 depicts Example configuration of SS blocks, SS bursts and SSburst sets/series.

Mobility and Beam Management in NR

In NR it has been agreed that there will be two levels of mobility, onewithout involving Radio Resource Control (RRC), also called intra-cellmobility, part of what is often called beam management, and another typeof mobility involving RRC, also called cell level mobility. Cell LevelMobility is described as follows in the TS 38.300 specifications.

Cell Level Mobility requires explicit RRC signalling to be triggered,i.e. handover. Handover signalling procedures adopt the same principleas Release 13 E-UTRAN as specified in 3GPP TS 36.300. For inter-gNBhandover, the signalling procedures consist of at least the followingelemental components illustrated in FIG. 5, Inter-gNB handoverprocedures.

1. The source gNB initiates handover and issues a Handover Request overthe Xn interface. The Xn interface is the interface between gNBs.

2. The target gNB performs admission control and provides an RRCconfiguration as part of the Handover Acknowledgement.

3. The source gNB provides the RRC configuration to the UE in theHandover Command. The Handover Command message includes at least cell IDand all information required to access the target cell so that the UEcan access the target cell without reading system information. For somecases, the information required for contention based and contention freerandom access can be included in the Handover Command message. Theaccess information to the target cell may include beam specificinformation, if any.

4. The UE moves the RRC connection to the target gNB and replies theHandover Complete.

The handover mechanism triggered by RRC requires the UE at least toreset the Medium Access Control (MAC) entity and re-establish RLC. ForData Radio Bearers (DRBs) using RLC Acknowledged Mode (AM) mode, PacketData Convergence Protocol (PDCP) can either be re-established togetherwith a security key change or initiate a data recovery procedure withouta key change. For DRBs using RLC Acknowledged Mode (UM) mode and forSRBs, PDCP can either be re-established together with a security keychange or remain as it is without a key change.

Data forwarding, in-sequence delivery and duplication avoidance athandover can be guaranteed when the target gNB uses the same DRBconfiguration and QoS flow to DRB mapping as the source gNB.

Beam Level Mobility does not require explicit RRC signalling to betriggered—it is dealt with at lower layers—and RRC is not required toknow which beam is being used at a given point in time.

Beam level mobility is achieved by what is often called beam managementprocedures. It has been agreed in RAN1 that the primary Reference Signal(RS) to be used for beam management is Channel State Information(CSI)-RS, which can be configured via dedicated signalling.

CSI-RS Configuration in LTE and Usage of the MAC Control Element (CE)Activation/Deactivation

In LTE, until Release 13, all reference signals that UE uses for CSIcalculation, CRS, CSI-RS, were non-precoded such that UE is able tomeasure the raw channel and calculated feedback including preferredprecoding matrix based on that. As the number of Tx antennas increases,the amount of feedback becomes larger. In LTE Release 10, when supportfor 8Tx closed loop precoding was introduced, a double codebook approachwas introduced where UE first selects a wideband coarse precoder andthen per subband a second codeword.

Another possible approach is that a network node such as the eNBbeamforms the reference signal and UE calculates feedback on top ofthat. This approach was adopted in LTE Release 13 and one option for theFull-Dimension (FD)-MIMO as described in the next section.

Release 13 FD-MIMO specification in LTE supports an enhanced CSI-RSreporting called Class B for beamformed CSI-RS. Therein, an LTERRC_CONNECTED UE may be configured with K CSI-RS resources (where 8>K>1)where it may be 1, 2, 4 or 8 ports for each CSI-RS resource. Each CSI-Rsresource is associated with a CSI-RS Resource Indicator (CRI). The UEreports CRI to indicate the preferred CSI-RS resource, along with theRI/CQI/PMI based on legacy codebook (i.e. Rel-12).

For Release-14 enhanced Full-Dimension (eFD)-MIMO aperiodic CSI-RS wasintroduced with two different sub-flavors. The CSI-RS resources areconfigured for the UE as in LTE Release 13 and if the set of K CSI-RSresources is configured to work as aperiodic, aperiodic-aperiodic ormulti shot-aperiodic. UE waits for MAC CE activation for N out of KCSI-RS resources. For aperiodic-aperiodic, UE waits in addition to MACCE, a DCI activation of the CSI-RS resource before reporting.

Activation/deactivation command is specified in 3GPP TS36.321 whereSection 5.19 describes:

The network may activate and deactivate the configured CSI-RS resourcesof a serving cell by sending to the UE the Activation/Deactivation ofCSI-RS resources MAC control element described in sub clause 6.1.3.14.The configured CSI-RS resources are initially deactivated uponconfiguration and after a handover. In FIG. 6, the eNB sends BeamformedCSI-RS 1, 2 and 3. The UE measures these CSI-RS 1, 2 and 3 and sincebeam CSI RS 2 gives the best result, the UE reports that CRI=2 andRI/CQI/PMI that is measured on CSI-RS 2.

Section 6.1.3.14 in TS 36.321 describes:

The Activation/Deactivation of CSI-RS resources MAC control element isidentified by a MAC Protocol Data Unit (PDU) subheader with LogicalChannel Identifier (LCID) as specified in table 6.2.1-1. It has variablesize as the number of configured CSI process (N) and is defined inFigure 6.1.3.14-1. Activation/Deactivation CSI-RS command is defined inFigure 6.1.3.14-2 and activates or deactivates CSI-RS resources for aCSI process. Activation/Deactivation of CSI-RS resources MAC controlelement applies to the serving cell on which the UE receives theActivation/Deactivation of CSI-RS resources MAC control element.

The Activation/Deactivation of CSI-RS resources MAC control elements isdefined as follows:

-   -   Ri: this field indicates the activation/deactivation status of        the CSI-RS resources associated with CSI-RS-ConfigNZPId i for        the CSI-RS process. The Ri field is set to “1” to indicate that        CSI-RS resource associated with CSI-RS-ConfigNZPId i for the        CSI-RS process shall be activated. The Ri field is set to “0” to        indicate that the CSI-RS-ConfigNZPId i shall be deactivated.        ConfigNZPId means configuration Non Zero Power Identifier.        Figure 6.1.3.14-1 is shown in FIG. 7 and depicts        activation/Deactivation of CSI-RS resources MAC Control Element.        Figure 6.1.3.14-2 is shown in FIG. 8 and depicts        activation/Deactivation CSI-RS command.

The MAC CE activation was introduced in LTE to be able to configure moreCSI-RS resources for a UE that the UE is able to support feedback for asthe MAC CE would selective activate up to max CSI-RS resourcessupported. Then, without the need to reconfigure by RRC, network mayactivate another set among the resources configured for the UE.

Radio Link Monitoring (RLM) in LTE and Potential Differences in NR

The purpose of the RLM function in the UE is to monitor the downlinkradio link quality of the serving cell in RRC_CONNECTED state and is inLTE based on the Cell-Specific Reference Signals (CRS), which is alwaysassociated to a given LTE cell and derived from the Physical CellIdentifier (PCI). This in turn enables the UE when in RRC_CONNECTEDstate to determine whether it is in-synchronization (sync) orout-of-sync with respect to its serving cell.

The UE's estimate of the downlink radio link quality is compared without-of-sync and in-sync thresholds, Qout and Qin respectively, for thepurpose of RLM. These thresholds are expressed in terms of the BlockError Rate (BLER) of a hypothetical Physical Downlink Control Channel(PDCCH) transmission from the serving cell. Specifically, Qoutcorresponds to a 10% BLER while Qin corresponds to a 2% BLER. The samethreshold levels are applicable with and without Discontinuous Reception(DRX).

The mapping between the CRS based downlink quality and the hypotheticalPDCCH BLER is up to the UE implementation. However, the performance isverified by conformance tests defined for various environments. Also theUE may calculate the downlink quality based on the CRS received over thewhole band since UE does not necessarily know where PDCCH is going to bescheduled.

FIG. 9 depicts how PDCCH may be scheduled anywhere over the wholedownlink transmission bandwidth.

When no DRX is configured, out-of-sync occurs when the downlink radiolink quality estimated over the last 200 ms period becomes worse thanthe threshold Qout. Similarly, without DRX the in-sync occurs when thedownlink radio link quality estimated over the last 100 ms periodbecomes better than the threshold Qin. Upon detection of out-of-sync,the UE initiates the evaluation of in-sync. The occurrences ofout-of-sync and in-sync are reported internally by the UE's physicallayer to its higher layers, which in turn may apply layer 3 (i.e. higherlayer) filtering for the evaluation of Radio Link Failure (RLF). FIG. 10depicts Higher layer RLM procedures in LTE.

When DRX is in use, in order to enable sufficient UE power saving theout-of-sync and in-sync evaluation periods are extended and depend uponthe configured DRX cycle length. The UE starts in-sync evaluationwhenever out-of-sync occurs. Therefore, the same period, also referredto as TEvaluate_Qout_DRX, is used for the evaluation of out-of-sync andin-sync. However, upon starting an RLF timer, referred to as T310, untilits expiry, the in-sync evaluation period is shortened to 100 ms, whichis the same as without DRX. If the timer T310 is stopped due to N311consecutive in-sync indications, the UE performs in-sync evaluationaccording to the DRX based period (TEvaluate_Qout_DRX). N311 is referredto as the in-sync counter.

The whole methodology used for RLM in LTE, i.e. measuring the CRS to“estimate” the PDCCH quality, relies on the fact that the UE isconnected to an LTE cell which is the single connectivity entitytransmitting PDCCH and CRSs.

Beam Recovery

In NR, a procedure called beam recovery is being defined. In beamrecovery, an RRC_CONNECTED UE would perform measurements associated tothe quality of the serving link and, if that quality goes below a giventhreshold, the UE would perform beam recovery. The procedure aims tosolve the situation where the TX and RX beams of the gNodeB and the UEhave become misaligned, but where there are additional beams that couldbe used to maintain the connection between the gNodeB and the UE.

The beam failure recovery procedure includes the following aspects:

-   -   Beam failure detection: here the UE monitors a certain periodic        reference signal (RS) to estimate the quality of the serving        link. Once the quality of that link falls below a certain        threshold, the UE initiates beam recovery.    -   New candidate beam identification. Once beam failure has been        detected, the UE tries to identify a new beam that would provide        adequate quality. The UE then searches for a specific RS, which        is transmitted from the same node, but in difference candidate        beams. During this search procedure, the UE may also change its        RX beam.    -   Beam failure recovery request transmission. Once a new candidate        beam has been found, the UE transmits an UL signal using certain        UL resources. The gNodeB is prepared to receive the UL signal in        these UL resources, and can determine which candidate beam the        UE selected based on the receive UL signal.    -   When the gNodeB has received the beam failure recovery request,        it sends a DL response to indicate to the UE that it received        the request, using the knowledge of the new beam.    -   UE monitors gNB response for beam failure recovery request. Once        the UE has successfully received the response, the beam recovery        is complete.

In NR, a few options are being discussed with respect to the periodic RSthe UE monitors to estimate the quality of the serving link:

-   -   The network can configure the UE to perform beam monitoring        based on signals transmitted in the SS Block.    -   The network may also configure the UE to perform beam monitoring        based on the channel state information reference signal (CSI-RS)

The same options are being discussed as the reference signal used forcandidate beam identification. At least for CSI-RS, differentconfigurations may be used for the two purposes.

One candidate for the UL signal used for the beam failure recoveryrequest is physical random access channel (PRACH), the same type ofsignal used during initial access. To transmit using the PRACH, the UEselects one sequence out of the available PRACH sequences. Hence, thePRACH does not carry any payload. The information is conveyed bychoosing different preambles. During initial access, the UE randomlychooses one PRACH sequence from a large set of available PRACHsequences. In other cases, e.g., during handover, the UE may choose aPRACH sequence from a set with only one element.

The beam recovery procedure is somewhat similar to the RLF and RRCreestablishment procedures. The main difference is that beam recovery isa faster procedure. Also, the connection is reestablished with theserving cell: the UE will not search for other cells.

Through beam recovery, the UE can quickly reconnect with the servingcell.

SUMMARY

An object of embodiments herein is therefore to improve the performanceof a radio communications network using beams.

According to a first aspect of embodiments herein, the object isachieved by a method performed by a User Equipment (UE) for monitoring abeam transmitted by a base station in a radio communications network.The base station is serving the UE. The UE monitors a reference signalrelated to the beam, from the base station. Each time a quality of thereference signal is below a first threshold, the UE generates anOut-Of-Synchronization (OOS) event

When the number of OOS events reaches an OOS Beam Failure Detection(BFD) threshold, the UE triggers a beam recovery preparation procedure,and

when the number of OOS events reaches an OOS Radio Link Monitoring(RLM), threshold, the UE starts an RLF timer.

According to a second aspect of embodiments herein, the object isachieved by a method performed by a base station for configuring a UE tomonitor a beam transmitted by the base station in a radio communicationsnetwork. The base station is serving the UE. The base station configuresthe UE to:

-   -   monitor a reference signal related to the beam, from the base        station,    -   each time a quality of the reference signal is below a first        threshold, generate an Out-Of-Synchronization, OOS, event,    -   when the number of OOS events reaches an OOS Beam Failure        Detection, BFD, threshold, trigger a beam recovery preparation        procedure, and    -   when the number of OOS events reaches an OOS Radio Link        Monitoring, RLM, threshold, start an RLF timer.

According to a third aspect of embodiments herein, the object isachieved by a User Equipment, UE, for monitoring a beam transmitted by abase station in a radio communications network. The base station isserving the UE. The UE is configured to:

-   -   monitor a reference signal related to the beam, from the base        station,    -   each time a quality of the reference signal is below a first        threshold, generate an Out-Of-Synchronization, OOS, event,    -   when the number of OOS events reaches an OOS Beam Failure        Detection, BFD, threshold, trigger a beam recovery preparation        procedure, and    -   when the number of OOS events reaches an OOS Radio Link        Monitoring, RLM, threshold, start an RLF timer.

According to a fourth aspect of embodiments herein, the object isachieved by a base station for configuring a UE to monitor a beamtransmitted by the base station in a radio communications network. Thebase station is serving the UE. The base station is adapted to configurea UE to:

-   -   monitor a reference signal related to the beam, from the base        station,    -   each time a quality of the reference signal is below a first        threshold, generate an Out-Of-Synchronization, OOS, event,    -   when the number of OOS events reaches an OOS Beam Failure        Detection, BFD, threshold, trigger a beam recovery preparation        procedure,    -   when the number of OOS events reaches an OOS Radio Link        Monitoring, RLM, threshold, start an RLF timer.

An advantage of embodiments herein is that they provide a measurementframework for beam failure detection and radio link monitoring whichsimplifies the UE monitoring actions, which in turn may simplify UEimplementation, the amount of network configuration and the amount ofmeasurements to be performed by the UE which improve the performance ofa radio communications network using beams. This may further e.g. leadto reduce the battery consumption in the UE.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of embodiments herein are described in more detail withreference to attached drawings in which:

FIG. 1 is a schematic block diagram according to prior art.

FIG. 2 is a schematic diagram according to prior art.

FIG. 3 is a schematic diagram according to prior art.

FIG. 4 is a schematic block diagram according to prior art.

FIG. 5 is a sequence diagram illustrating a method according toaccording to prior art.

FIG. 6 is a schematic block diagram according to prior art.

FIG. 7 is a schematic block diagram according to prior art.

FIG. 8 is a schematic block diagram according to prior art.

FIG. 9 is a schematic block diagram according to prior art.

FIG. 10 is a schematic block diagram according to prior art.

FIG. 11 is a schematic block diagram depicting embodiments of a radiocommunications network.

FIG. 12a is a flowchart illustrating embodiments of method in a UE.

FIG. 12b is a flowchart illustrating embodiments of method in a UE.

FIG. 13 is a flowchart illustrating embodiments of method in a basestation

FIG. 14 is a schematic block diagram illustrating embodiments of a UE

FIG. 15. is a schematic block diagram illustrating embodiments of a basestation.

FIG. 16 schematically illustrates a telecommunication network connectedvia an intermediate network to a host computer.

FIG. 17 is a generalized block diagram of a host computer communicatingvia a base station with a user equipment over a partially wirelessconnection.

FIGS. 18 to 21 are flowcharts illustrating methods implemented in acommunication system including a host computer, a base station and auser equipment.

DETAILED DESCRIPTION

As a part of developing embodiments herein a problem will first beidentified and discussed.

Beam recovery has been discussed for the new 5G radio (NR) as a way toenable the UE to detect a downlink problem in the serving cell andtrigger an action to indicate the network that the DL beam the networkmight assume as the best (i.e. the DL beam the network would have usedfor PDCCH transmission to contact the UE e.g. to schedule data orcontrol information) is either not good enough any longer or not thebest any longer. Concerning that beam recovery procedure, the followinghas been agreed in RAN1 #88, in 3GPP TS 38.213, section 6.

Agreements:

-   -   UE Beam failure recovery mechanism includes the following        aspects        -   Beam failure detection        -   New candidate beam identification        -   Beam failure recovery request transmission        -   UE monitors gNB response for beam failure recovery request    -   Beam failure detection        -   UE monitors beam failure detection RS to assess if a beam            failure trigger condition has been met        -   Beam failure detection RS at least includes periodic CSI-RS            for beam management    -   SS-block within the serving cell can be considered, if SS-block        is also used in beam management as well        -   For Further Study (FFS): Trigger condition for declaring            beam failure    -   New candidate beam identification        -   UE monitors beam identification RS to find a new candidate            beam        -   Beam identification RS includes    -   Periodic CSI-RS for beam management, if it is configured by NW    -   Periodic CSI-RS and SS-blocks within the serving cell, if        SS-block is also used in beam management as well    -   Beam failure recovery request transmission        -   Information carried by beam failure recovery request            includes at least one followings    -   Explicit/implicit information about identifying UE and new gNB        TX beam information    -   Explicit/implicit information about identifying UE and whether        or not new candidate beam exists    -   FFS:    -   Information indicating UE beam failure    -   Additional information, e.g., new beam quality        -   Down-selection between the following options for beam            failure recovery request transmission    -   PRACH    -   PUCCH    -   PRACH-like (e.g., different parameter for preamble sequence from        PRACH)        -   Beam failure recovery request resource/signal may be            additionally used for scheduling request    -   UE monitors a control channel search space to receive gNB        response for beam failure recovery request        -   FFS: the control channel search space can be same or            different from the current control channel search space            associated with serving BPLs        -   FFS: UE further reaction if gNB does not receive beam            failure recovery request transmission

There are a certain number of problems to be solved that were notdiscussed in RAN1 or RAN2 such as:

Some embodiments herein address these issues and provides a set ofmethods for each of these.

As mentioned above, an object of embodiments herein is therefore toimprove the performance of a radio communications network using beams.

Some embodiments herein relate to Beam recovery procedures.

Embodiments herein comprise a set of method executed by a UE and anetwork such as a base station, comprising a set of networkconfigurations and UE actions enabling the UE to monitor a possiblefailure of a beam in a serving cell. This may according to exampleembodiments herein mean that the UE estimates that the network is notable to efficiently reach the UE with PDCCH or any other downlinkcontrol channel; triggers UE actions to notify the network what could bea new beam to be used in the downlink for PDCCH; trigger the network totransmit a notification to the UE concerning whether beam recovery wassuccessful or not and what needs to be updated at the UE based on thenewly selected beam, e.g. beam management related configuration; UEactions upon that network response; network actions concerning how theUE could be reached before and after beam recovery is notified.

Embodiments herein relate to wireless communication networks in general.FIG. 11 is a schematic overview depicting a radio communications network100. The radio communications network 100 comprises one or more RANs andone or more CNs. The radio communications network 100 may use a numberof different technologies, such as Wi-Fi, Long Term Evolution (LTE),LTE-Advanced, 5G, New Radio (NR), Wideband Code Division Multiple Access(WCDMA). Global System for Mobile communications/enhanced Data rate forGSM Evolution (GSM/EDGE), Worldwide Interoperability for MicrowaveAccess (WiMAX), or Ultra Mobile Broadband (UMB), just to mention a fewpossible implementations. Embodiments herein relate to recent technologytrends that are of particular interest in a 5G context, however,embodiments are also applicable in further development of the existingwireless communication systems such as e.g. WCDMA and LTE.

In the wireless communication network 100, wireless devices e.g. a UE120 such as a mobile station, a non-access point (non-AP) STA, a STA,and/or a wireless terminal, communicate via one or more Access Networks(AN), e.g. RAN, to one or more core networks (CN). It should beunderstood by the skilled in the art that “wireless device” is anon-limiting term which means any terminal, wireless communicationterminal, user equipment, Machine Type Communication (MTC) device,Device to Device (D2D) terminal, or node e.g. smart phone, laptop,mobile phone, sensor, relay, mobile tablets or even a small base stationcommunicating within a cell.

The radio communications network 100 comprises a base station 110providing radio coverage over a geographical area, a service area 11,which may also be referred to as a beam or a beam group of a first radioaccess technology (RAT), such as 5G, LTE, Wi-Fi or similar. The basestation 110 may be a transmission and reception point e.g. a radioaccess network node such as a Wireless Local Area Network (WLAN) accesspoint or an Access Point Station (AP STA), an access controller, a basestation, e.g. a radio base station such as a NodeB, an evolved Node B(eNB, eNode B), a 5G NodeB (gNB, gNodeB), a base transceiver station, aradio remote unit, an Access Point Base Station, a base station router,a transmission arrangement of a radio base station, a stand-alone accesspoint or any other network unit capable of communicating with a wirelessdevice within the service area served by the base station 110 dependinge.g. on the first radio access technology and terminology used. The basestation 110 may be referred to as a serving radio network node andcommunicates with the UE 120 with Downlink (DL) transmissions to the UE120 and Uplink (UL) transmissions from the UE 120.

Methods for configuring the UE 120 to monitor a beam transmitted thebase station 110 in the radio communications network 100, is performedby the base station 110. As an alternative, a Distributed Node (DN) andfunctionality, e.g. comprised in a cloud 130 as shown in FIG. 11, may beused for performing or partly performing the methods.

Example embodiments of a flowchart depicting embodiments of a methodperformed by the UE 120, for monitoring a beam transmitted by the basestation 110 in the radio communications network 100 is depicted in FIG.12a . The base station 110 is serving the UE 120. The method will firstbe described in a general way, which will be explained with more detailsand examples later on. The method comprises one or more of the followingactions which actions may be taken in any suitable order. Actions thatare optional are presented in dashed boxes in FIG. 12 a.

Action 1201

This action is optional. The UE 120 may first be configured e.g. byreceiving a configuration from the network such as the base station 110.Thus, in some embodiments, the UE 120 receives a configuration from thebase station 110. The configuration comprises at least one referencesignal related to the beam. The reference signal is to be monitored bythe UE 120 for Beam Failure Detection (BFD), and cell-level Radio LinkMonitoring (RLM).

Action 1202

The UE 120 monitors a reference signal related to the beam. The beam issent from the base station 110. As mentioned above, the reference signalis to be monitored by the UE 120 for BFD and for cell-level RLM.

Action 1203

To be able to detect a beam failure, the UE 120 should generateOut-Of-Synchronization (OOS) events based the quality of the referencesignal such as measured CSI-RS. Thus, each time a quality of thereference signal is below a first threshold, also referred to asThr-oos, the UE 120 generates an OOS event.

Action 1204

This action is optional. To detect some kind of recovery, the UE 120 maygenerate IS events based the quality of the reference signal such asmeasured CSI-RS.

Each time a quality of the reference signal is above a second threshold,also referred to as Thr-is, the UE 120 may in some embodiments, generatean In-Synchronization (IS) event.

Action 1205

When the number of OOS events reaches an OOS BFD threshold also referredto as N-oos-bfd, the UE 120 triggers a beam recovery preparationprocedure. Once the UE 120 has detected N-oos-bfd OOS indications, theUE 120 may determine that there is a problem with the current beam, andstarting the preparation to recover the beam.

In some embodiments, the triggering of the beam recovery preparationprocedure is performed when furthermore, the number of IS events isbelow an IS BFD threshold also referred to as N-is-bfd. Since the UE 120has detected less N-s-bfd IS indications, the UE 120 may determine thatthere is a problem with the current beam, and starting the preparationto recover the beam.

Action 1206 a

When the number of OOS events reaches an OOS RLM threshold also referredto as N-oos-rlm, the UE 120 starts an RLF timer also referred to asTimer-oos-rlm.

In some embodiments, the starting OF the RLF timer is performed whenfurthermore, the number of IS events is below an IS RLM threshold alsoreferred to as N-is-rlm.

In some embodiments, the starting of the RLF timer further comprisesstarting to count IS events. This may be used in some embodiments todecide whether to declare RLF or just stop the timer.

Action 1206 b

This is optional alternative. If the RLF timer expires while the numberof counted IS events have not reached the IS RLM threshold the UE 120may declare RLF.

Action 1207

This is optional alternative. If the number of counted IS events reachesthe IS RLM threshold while the RLF timer is running the UE 120 may stopthe RLF timer.

The OOS RLM threshold and the OOS BFD threshold may be configured suchthat the beam recovery preparation procedure is triggered beforedeclaring Radio Link Failure. Further, the IS RLM threshold and the ISBFD threshold may be configured such that the beam recovery preparationprocedure is triggered before declaring Radio Link Failure.

Example embodiments of a flowchart depicting embodiments of a methodperformed by the UE 120, e.g. for monitoring a beam transmitted by thebase station 110 in the radio communications network 100 is depicted inFIG. 12b . The base station 110 is serving the UE 120. The methodcomprises one or more of the following actions which actions may betaken in any suitable order:

Monitoring 1202 a reference signal related to the beam, from the basestation 110,

each time a quality of the reference signal is below a first threshold,generating 1203 an Out-Of-Synchronization, OOS, event,

each time a quality of the reference signal is above a second threshold,generating 1204 an In-Synchronization, IS, event,

when the number of OOS events reaches an OOS Beam Failure Detection,BFD, threshold, and possibly the number of IS events is below an IS BFDthreshold, triggering 1205 a beam recovery preparation procedure,

when the number of OOS events reaches an OOS Radio Link Monitoring, RLM,threshold and possibly the number of IS events is below an IS RLMthreshold, declaring 1206 Radio Link Failure related to the beam,

wherein OOS RLM threshold and the OOS BFD threshold and possibly thewherein IS RLM threshold and the IS BFD threshold are configured suchthat the beam recovery preparation procedure is triggered beforedeclaring Radio Link Failure.

Example embodiments of a flowchart depicting embodiments of a methodperformed by the base station 110 for configuring the UE 120 to monitora beam transmitted the base station 110 in the radio communicationsnetwork 100, is depicted in FIG. 13. The base station 110 is serving theUE 120. The method comprises one or more of the following actions whichactions may be taken in any suitable order.

This method configures the UE 120 to perform the method actionsdescribed above.

Action 1301

The base station 110 configures the UE 120 to:

-   -   Monitor a reference signal related to the beam from the base        station 110.    -   Each time a quality of the reference signal is below a first        threshold, generate an OOS event.    -   When the number of OOS events reaches an OOS BFD threshold,        trigger a beam recovery preparation procedure, and when the        number of OOS events reaches an OOS RLM threshold, start an RLF        timer.

In some embodiments, the base station 110 further configure the UE 120to, each time a quality of the reference signal is above a secondthreshold, generate an IS event.

In some of these embodiments, the base station 110 further configuresthe UE 120 to trigger the beam recovery preparation procedure to beperformed when furthermore, the number of IS events is below an IS BFDthreshold.

The base station 110 may configure the UE 120 to start the RLF timerwhen furthermore, the number of IS events is below an IS RLM threshold.

In some embodiments, the base station 110 configures the UE 120 to startto count IS events when starting the RLF timer and to act according to:

If the RLF timer expires while the number of counted IS events have notreached the IS RLM threshold, declaring Radio Link Failure, and if thenumber of counted IS events reaches the IS RLM threshold while the RLFtimer is running, stop the timer.

The OOS RLM threshold and the OOS BFD threshold may be configured suchthat the beam recovery preparation procedure is triggered beforedeclaring Radio Link Failure.

Further, the IS RLM threshold and the IS BFD threshold may be configuredsuch that the beam recovery preparation procedure is triggered beforedeclaring Radio Link Failure.

Further Extensions and Variations

The UE discussed below may refer to the UE 120 and the network discussedbelow may refer to the base station 110. The example embodiments may becombined in any suitable way.

Example embodiments herein e.g. comprises the following steps from theUE 120 which is referred to as the UE below and the base station 110which is referred to as the network below:

Part 1, RS Configuration for Beam Failure Detection and Radio LinkMonitoring

An RRC_CONNECTED UE may be configured, e.g. via dedicated signaling,with at least one CSI-RS resource to be monitored for cell-level radiolink monitoring and beam failure detection. That configuration maycomprise one or multiple resources where the particular CSI-RS istransmitted. In that context, a resource may be in the time domain, e.g.one or multiple OFDM symbol(s), the frequency domain and/or sequencedomain, e.g. a given seed such as a virtual cell ID. The UE may not needto be aware how that CSI-RS resource maps to a particular beam in thedownlink transmitted by the network i.e. the UE simply is configure tomonitor the quality of that particular resource.

On the network side, that configured CSI-RS is beamformed similarly to afallback PDCCH i.e. that is how the network should reach the UE if thenetwork does not have any more granular information such as a narrowbeam used for PDSCH transmission. On the network side, the exactconfiguration for these two purposes, i.e. beam failure detection andradio link monitoring, is decided based on the initial downlink beamknowledge the network may obtain during the random access procedureduring state transition from RRC_IDLE to RRC_CONNECTED or after ahandover. A UE is in RRC_CONNECTED when an RRC connection has beenestablished. If this is not the case, i.e. no RRC connection isestablished, the UE is in RRC_IDLE or RRC_INACTIVE state. In otherwords, after random access, e.g. based on a beam selection using an RStransmitted in the SS Block, the network knows the best DL beam the UEis covered by. There may be two cases depending on networkconfiguration:

-   -   If the network is performing beam sweeping of periodic CSI-RS(s)        to cover the cell, the network may select one of the already        transmitted DL beams based on that input i.e. the network will        in fact select a CSI-RS resource transmitting in that direction.        By doing that, the network makes sure that the UE will monitor a        CSI-RS resource transmitted in a DL beam that is the best        according to the UE selection during random access. The network        may choose to use that configuration if the cell is loaded and        many UEs will require to monitor many beams all over the cell        coverage for these purposes.    -   If the network is NOT performing beam sweeping of periodic        CSI-RS(s) to cover the cell, the network has the flexibility to        perform beam tracking. In that case, the network may choose any        available resource, time, frequency, sequence, to transmit in        that selected beam e.g. based on UE input during random access.        The network may choose to use that configuration if the cell is        not loaded to avoid the sweeping in all directions that may        create interference to other cells.

Part 2, Configuration for Triggering Beam Failure Detection and RadioLink Monitoring and UE Monitoring Actions

The UE is configured with different criteria to trigger beam failuredetection and radio link monitoring, although the same RS configurationmay be used for both purposes as long as the UE is within the coverageof a given beam.

To detect a beam failure, the UE should generate out-of-sync (OOS)events based the quality of the measured reference signal, e.g., CSI-RS.To detect some kind of recovery, the UE should generate in-sync (IS)events based the quality of the measured reference signal, e.g., CSI-RS.There may be different ways these events may be generated. An OOS eventmay, e.g., be generated when the quality of the reference signal isbelow a certain threshold. An IS event may, e.g., be generated when thequality of the reference signal is above a certain threshold

In some embodiments the UE is configured by the network with a thresholdThr-oos where the threshold indicates that if quality of the configuredreference signal, e.g., CSI-RS falls below that value the UE shouldgenerate an OSS event and start counting them. The threshold Thr-oos isalso referred to as the first threshold herein. Similarly, the UE isconfigured by the network with a threshold Thr-is where the thresholdindicates that if the quality of the configured reference signal, e.g.,CSI-RS goes above that value the UE should generate an IS event andstart counting them. The threshold Thr-is is also referred to as thesecond threshold herein.

In some other embodiments the UE implementation defines internalthresholds Thr-oos and Thr-is that maps a given PDCCH BLER, e.g. 2%, inpre-defined measured intervals for a given accuracy. The thresholdThr-oos indicates that if quality of the configured reference signal,e.g., CSI-RS falls below that value the UE should generate an OOS eventand start counting them. That is an initial indication of beam failure.The threshold Thr-is indicates that if quality of the configured CSI-RSgoes above that value the UE should generate an IS event and startcounting them.

The UE is also configured with at least some of the following parametersrelated to the triggering of beam failure detection and radio linkfailure detection wherein “N” in the parameters below means “number”.

-   -   N-oos-bfd: A beam recovery preparation procedure, which will be        described later, should be triggered when the number of OOS        events reach this value N-oos-bfd. That may be the start of a        timer that is initiated and, once expired, the UE may declare        beam failure detection.    -   Timer-oos-bfd: This timer is started once the number of OOS        events reached the value N-oos-bfd. Once that timer starts, the        UE should start monitoring the number of in-sync events. There        may also be a threshold associated to that, either configurable        by the network or defined based on requirements related to the        PDCCH quality, such as e.g. a 2% BLER for a given accuracy and        measurement intervals. Notice that if network wants to make the        UE immediately trigger beam recovery once N-oos-bfd is reached,        that timer may be set to zero. Alternatively, another embodiment        may consider that the timer does not exist.    -   N-is-bfd: After Timer-oos-bfd starts, the UE should keep        monitoring the quality of the configured CSI-RS and the        occurrence of IS events. If the number of IS events goes above        that value, the timer should be stopped and the UE should leave        the condition to enter beam recovery procedure. If the timer is        set of ZERO, that parameter does not need to be configured. In        one embodiment without the parameter Timer-oos-bfd this        parameter also does not need to exist.    -   N-oos-rlm: N-oos-rlm is similar to N310 in LTE. An RLF timer        should be started when the number of OOS events reach that        value. When N-oos-bfd is reached, the timer Timer-oos-bfd will        start and the number of OOS events will kept being counted. Note        that this value may preferably be configured higher than        N-oos-bfd. That parameter is equivalent to the N310 parameter in        LTE, and the RLF timer is equivalent to T310 in LTE.        -   If N-oos-rlm is reached while the timer Timer-oos-bfd is            running, the UE should wait for the timer to finish before            RLF is declared. That gives the UE 120 an opportunity to            finish its beam recovery attempt(s) within the same cell            before RLF is declared.    -   Timer-oos-rlm: This timer is started once the number of OOS        events reached the value N-oos-rlm. Once the timer starts the UE        starts to monitors IS events. Notice that this value should be        configured higher >than N-oos-bfd. While that timer is running        the UE is still allowed to perform beam recovery procedures        within the same cell according to a well-defined behavior. In        some embodiments, while that timer is running, the UE should try        a maximum number of attempts before stopping for a back-off time        and try again. The UE may also use random access power ramp-up        actions such as change of Tx beam, etc. A successful attempt may        be perceived in the higher layers by incoming IS events as an        effect of a beam or beam pair switching from the network side        for the configured CSI-RS. When the timer Timer-oos-rlm expires        the UE declares RLF.    -   N-is-rlm: The RLF timer, equivalent to T310 in LTE, should be        stopped when the number of IS events reach this value N-is-rlm.

Notice that lower layers might always provide to higher layers at the UEthe IS and OOS events. However, while the higher layers are alwaysmonitoring the OOS events to possibly trigger Timer-oos-rlm, the ISevents are only counter once the timer is triggered.

Part 3, UE Monitoring Actions

Once the UE is configured with the parameters described in Part 2 the UEwill monitor the configured reference signal, e.g., CSI-RS and compareits quality with a threshold. If quality is <than Thr-oos the UE shouldgenerate OOS events. That event is indicated to the layer responsiblefor RLM, such as e.g. RRC, and for beam failure detection, such as e.g.MAC, Physical (PHY) or RRC The layer at the UE responsible for beamfailure detection will monitor whether the number of OOS events reachN-oos-bfd while in parallel, the layer responsible for radio linkmonitoring will monitor whether the number of OOS events reachN-oos-rlm. Hence, these counters are started once the first OOS eventarrives. Notice that keeping two parallel counters is one simplifiedimplementation, while one could keep a single counter but monitor boththresholds e.g. if the same layer (or function at the UE) handles bothbeam failure detection and RLM procedures.

Actions of the Beam Failure Detection Layer

In one embodiment, when the number of OOS events reaches N-oos-bfd, theUE should declare the detection of beam failure and invoke a beamrecovery procedure. This is a quite simple solution.

In another embodiment, when the number of OOS events reaches N-oos-bfd,the UE starts a timer Timer-oos-bfd and starts to count IS events. Ifthe timer expires while the number of counted IS events have not reachedN-is-bfd, the UE should declare the detection of beam failure and invokea beam recovery procedure. If the number of counted IS events reachesN-s-bfd, while the timer is running, the UE should leave that conditionand stop the timer. This provides some time to the UE to recover withoutthe need to indicate the network and/or the network to recover based onL1 reporting not triggered by beam failure detection.

Note: The next part (Part 4)) will describe the UE actions upon beamfailure detection i.e. beam recovery procedure and network response tothat.

Actions of the Radio Link Monitoring Layer

In one embodiment, when the number of OOS events reaches N-oos-rlm theUE starts the timer Timer-oos-rlm and starts to count IS events. If thetimer expires while the number of counted IS events have not reachedN-is-rlm, the UE should declare RLF. If the number of counted IS eventsreaches N-is-rlm, while the timer is running, the UE should leave thatcondition, i.e. having the timer running, and stop the timer. The word“condition when used herein means” having the timer running.

To perform the method actions for monitoring a beam transmitted by thebase station 110 in the radio communications network 100, the UE 120 maycomprise the arrangement depicted in FIG. 14. The UE 120 is adapted tobe served by the base station 110.

The UE 120 is configured to, e.g. by means of a monitoring module 1410in the UE 120, monitor a reference signal related to the beam, from thebase station 110.

The UE 120 is configured to, e.g. by means of a generating module 1420in the UE 120, each time a quality of the reference signal is below afirst threshold, generate an OOS event.

The UE 120 is further configured to, e.g. by means of a triggeringmodule 1430 in the UE 120, when the number of OOS events reaches an OOSBFD threshold, trigger a beam recovery preparation procedure.

The UE 120 is further configured to, e.g. by means of the triggeringmodule 1430 in the UE 120, when the number of OOS events reaches an OOSRLM, threshold, start an RLF timer.

The UE 120 may further be configured to, e.g. by means of a receivingmodule 1450 in the UE 120, receive from the base station 110 aconfiguration comprising at least one reference signal related to thebeam, which reference signal is to be monitored by the UE 120 for BFD,and cell-level RLM.

The UE 120 may further be configured to, e.g. by means of the generatingmodule 1420 in the UE 120, each time a quality of the reference signalis above a second threshold, generate an IS event.

The UE 120 may further be configured to, e.g. by means of the triggeringmodule 1430 in the UE 120, trigger the beam recovery preparationprocedure when furthermore, the number of IS events is below an IS BFDthreshold.

The UE 120 may further be configured to, e.g. by means of the triggeringmodule 1430 in the UE 120, start the RLF timer when furthermore, thenumber of IS events is below an IS RLM threshold.

The UE 120 may further be configured to, e.g. by means of the triggeringmodule 1430 in the UE 120, start the RLF timer and to further start tocount IS events.

The UE 120 may further be configured to, e.g. by means of the declaringmodule 1440 in the UE 120, if the RLF timer expires while the number ofcounted IS events have not reached the IS RLM threshold, declare RadioLink Failure.

The UE 12 may further be configured to, e.g. by means of a processor1460 in the UE 120, if the number of counted IS events reaches the ISRLM threshold while the RLF timer is running, stop the RLF timer.

The OOS RLM threshold and the OOS BFD threshold may be adapted to beconfigured such that the beam recovery preparation procedure istriggered before declaring Radio Link Failure.

The IS RLM threshold and the IS BFD threshold may be adapted to beconfigured such that the beam recovery preparation procedure istriggered before declaring Radio Link Failure.

To perform the method actions for configuring the UE 120 to monitor abeam transmitted the a base station 110 in a radio communicationsnetwork 100, the base station 110 may comprise the arrangement depictedin FIG. 15. The UE 120 is adapted to be served by the base station 110.

The base station 110 is adapted to, e.g. by means of a configuringmodule 1510 in the UE 120, configure the UE 120 to:

-   -   Monitor a reference signal related to the beam, from the base        station 110.    -   Each time a quality of the reference signal is below a first        threshold, generate an OOS event.    -   When the number of OOS events reaches an OOS BFD threshold,        trigger a beam recovery preparation procedure, and    -   when the number of OOS events reaches an OOS RLM, threshold,        start an RLF timer.

The base station 110 may further be adapted to, e.g. by means of theconfiguring module 1510 in the UE 120, configure the UE 120 to, eachtime a quality of the reference signal is above a second threshold,generate an IS event.

The base station 110 may further be adapted to, e.g. by means of aconfiguring module 1510 in the UE 120, configure the UE 120 to triggerthe beam recovery preparation procedure to be performed whenfurthermore, the number of IS events is below an IS BFD threshold.

The base station 110 may further be adapted to, e.g. by means of aconfiguring module 1510 in the UE 120, configure the UE 120 to start theRLF timer when furthermore, the number of IS events is below an IS RLMthreshold.

The base station 110 may further be adapted to, e.g. by means of aconfiguring module 1510 in the UE 120, configure the UE 120 to start theRLF timer and to further start to count IS events.

The base station 110 may further be adapted to, e.g. by means of aconfiguring module 1510 in the UE 120, configure the UE 120 to, if theRLF timer expires while the number of counted IS events have not reachedthe IS RLM threshold, declare Radio Link Failure.

The base station 110 may further be adapted to, e.g. by means of aconfiguring module 1510 in the UE 120, configure the UE 120 to, if thenumber of counted IS events reaches the IS RLM threshold while the RLFtimer is running, stop the RLF timer.

The OOS RLM threshold and the OOS BFD may be adapted to be configuredsuch that the beam recovery preparation procedure is triggered beforedeclaring Radio Link Failure.

The IS RLM threshold and the IS BFD threshold may be adapted to beconfigured such that the beam recovery preparation procedure istriggered before declaring Radio Link Failure.

The UE 120 may comprise an Input and output Interface 1400 configured tocommunicate with the base station 110. The input and output interface1400 may comprise a wireless receiver (not shown) and a wirelesstransmitter (not shown).

The base station 110 may comprise an Input and output Interface 1500configured to communicate with the UE 120. The input and outputinterface 1500 may comprise a wireless receiver (not shown) and awireless transmitter (not shown).

The embodiments herein may be implemented through a respective processoror one or more processors, such as the respective processor 1520 of aprocessing circuitry in the base station 110 depicted in FIG. 15 andprocessor 1460 of a processing circuitry in the UE 120 depicted in FIG.14, together with respective computer program code for performing thefunctions and actions of the embodiments herein. The program codementioned above may also be provided as a computer program product, forinstance in the form of a data carrier carrying computer program codefor performing the embodiments herein when being loaded into therespective base station 110 and UE 120. One such carrier may be in theform of a CD ROM disc. It is however feasible with other data carrierssuch as a memory stick. The computer program code may furthermore beprovided as pure program code on a server and downloaded to therespective base station 110 and UE 120.

The base station 110 and UE 120 may further comprise respective a memory1470 1530 comprising one or more memory units. The memory comprisesinstructions executable by the processor in the respective base station110 and UE 120.

The memory is arranged to be used to store e.g. feedback options,information, data, configurations, and applications to perform themethods herein when being executed in the respective base station 110and UE 120.

In some embodiments, a respective computer program comprisesinstructions, which when executed by the respective at least oneprocessor, cause the at least one processor of the respective basestation 110 and UE 120 to perform the actions above.

In some embodiments, a respective carrier comprises the respectivecomputer program, wherein the carrier is one of an electronic signal, anoptical signal, an electromagnetic signal, a magnetic signal, anelectric signal, a radio signal, a microwave signal, or acomputer-readable storage medium.

With reference to FIG. 16, in accordance with an embodiment, acommunication system includes a telecommunication network 3210 e.g. aWLAN, such as a 3GPP-type cellular network, which comprises an accessnetwork 3211, such as a radio access network, and a core network 3214.The access network 3211 comprises a plurality of base stations 3212 a,3212 b, 3212 c, such as AP STAs NBs, eNBs, gNBs or other types ofwireless access points, each defining a corresponding coverage area 3213a, 3213 b, 3213 c. Each base station 3212 a, 3212 b, 3212 c isconnectable to the core network 3214 over a wired or wireless connection3215. A first user equipment (UE) such as a Non-AP STA 3291 located incoverage area 3213 c is configured to wirelessly connect to, or be pagedby, the corresponding base station 3212 c. A second UE 3292 such as aNon-AP STA in coverage area 3213 a is wirelessly connectable to thecorresponding base station 3212 a. While a plurality of UEs 3291, 3292are illustrated in this example, the disclosed embodiments are equallyapplicable to a situation where a sole UE is in the coverage area orwhere a sole UE is connecting to the corresponding base station 3212.

The telecommunication network 3210 is itself connected to a hostcomputer 3230, which may be embodied in the hardware and/or software ofa standalone server, a cloud-implemented server, a distributed server oras processing resources in a server farm. The host computer 3230 may beunder the ownership or control of a service provider, or may be operatedby the service provider or on behalf of the service provider. Theconnections 3221, 3222 between the telecommunication network 3210 andthe host computer 3230 may extend directly from the core network 3214 tothe host computer 3230 or may go via an optional intermediate network3220. The intermediate network 3220 may be one of, or a combination ofmore than one of, a public, private or hosted network; the intermediatenetwork 3220, if any, may be a backbone network or the Internet; inparticular, the intermediate network 3220 may comprise two or moresub-networks (not shown).

The communication system of FIG. 16 as a whole enables connectivitybetween one of the connected UEs 3291, 3292 and the host computer 3230.The connectivity may be described as an over-the-top (OTT) connection3250. The host computer 3230 and the connected UEs 3291, 3292 areconfigured to communicate data and/or signaling via the OTT connection3250, using the access network 3211, the core network 3214, anyintermediate network 3220 and possible further infrastructure (notshown) as intermediaries. The OTT connection 3250 may be transparent inthe sense that the participating communication devices through which theOTT connection 3250 passes are unaware of routing of uplink and downlinkcommunications. For example, a base station 3212 may not or need not beinformed about the past routing of an incoming downlink communicationwith data originating from a host computer 3230 to be forwarded (e.g.,handed over) to a connected UE 3291. Similarly, the base station 3212need not be aware of the future routing of an outgoing uplinkcommunication originating from the UE 3291 towards the host computer3230.

Example implementations, in accordance with an embodiment, of the UE,base station and host computer discussed in the preceding paragraphswill now be described with reference to FIG. 17. In a communicationsystem 3300, a host computer 3310 comprises hardware 3315 including acommunication interface 3316 configured to set up and maintain a wiredor wireless connection with an interface of a different communicationdevice of the communication system 3300. The host computer 3310 furthercomprises processing circuitry 3318, which may have storage and/orprocessing capabilities. In particular, the processing circuitry 3318may comprise one or more programmable processors, application-specificintegrated circuits, field programmable gate arrays or combinations ofthese (not shown) adapted to execute instructions. The host computer3310 further comprises software 3311, which is stored in or accessibleby the host computer 3310 and executable by the processing circuitry3318. The software 3311 includes a host application 3312. The hostapplication 3312 may be operable to provide a service to a remote user,such as a UE 3330 connecting via an OTT connection 3350 terminating atthe UE 3330 and the host computer 3310. In providing the service to theremote user, the host application 3312 may provide user data which istransmitted using the OTT connection 3350.

The communication system 3300 further includes a base station 3320provided in a telecommunication system and comprising hardware 3325enabling it to communicate with the host computer 3310 and with the UE3330. The hardware 3325 may include a communication interface 3326 forsetting up and maintaining a wired or wireless connection with aninterface of a different communication device of the communicationsystem 3300, as well as a radio interface 3327 for setting up andmaintaining at least a wireless connection 3370 with a UE 3330 locatedin a coverage area (not shown in FIG. 17) served by the base station3320. The communication interface 3326 may be configured to facilitate aconnection 3360 to the host computer 3310. The connection 3360 may bedirect or it may pass through a core network (not shown in FIG. 17) ofthe telecommunication system and/or through one or more intermediatenetworks outside the telecommunication system. In the embodiment shown,the hardware 3325 of the base station 3320 further includes processingcircuitry 3328, which may comprise one or more programmable processors,application-specific integrated circuits, field programmable gate arraysor combinations of these (not shown) adapted to execute instructions.The base station 3320 further has software 3321 stored internally oraccessible via an external connection.

The communication system 3300 further includes the UE 3330 alreadyreferred to. Its hardware 3335 may include a radio interface 3337configured to set up and maintain a wireless connection 3370 with a basestation serving a coverage area in which the UE 3330 is currentlylocated. The hardware 3335 of the UE 3330 further includes processingcircuitry 3338, which may comprise one or more programmable processors,application-specific integrated circuits, field programmable gate arraysor combinations of these (not shown) adapted to execute instructions.The UE 3330 further comprises software 3331, which is stored in oraccessible by the UE 3330 and executable by the processing circuitry3338. The software 3331 includes a client application 3332. The clientapplication 3332 may be operable to provide a service to a human ornon-human user via the UE 3330, with the support of the host computer3310. In the host computer 3310, an executing host application 3312 maycommunicate with the executing client application 3332 via the OTTconnection 3350 terminating at the UE 3330 and the host computer 3310.In providing the service to the user, the client application 3332 mayreceive request data from the host application 3312 and provide userdata in response to the request data. The OTT connection 3350 maytransfer both the request data and the user data. The client application3332 may interact with the user to generate the user data that itprovides. It is noted that the host computer 3310, base station 3320 andUE 3330 illustrated in FIG. 17 may be identical to the host computer3230, one of the base stations 3212 a, 3212 b, 3212 c and one of the UEs3291, 3292 of FIG. 16, respectively. This is to say, the inner workingsof these entities may be as shown in FIG. 17 and independently, thesurrounding network topology may be that of FIG. 16.

In FIG. 17, the OTT connection 3350 has been drawn abstractly toillustrate the communication between the host computer 3310 and the useequipment 3330 via the base station 3320, without explicit reference toany intermediary devices and the precise routing of messages via thesedevices. Network infrastructure may determine the routing, which it maybe configured to hide from the UE 3330 or from the service provideroperating the host computer 3310, or both. While the OTT connection 3350is active, the network infrastructure may further take decisions bywhich it dynamically changes the routing (e.g., on the basis of loadbalancing consideration or reconfiguration of the network).

The wireless connection 3370 between the UE 3330 and the base station3320 is in accordance with the teachings of the embodiments describedthroughout this disclosure. One or more of the various embodimentsimprove the performance of OTT services provided to the UE 3330 usingthe OTT connection 3350, in which the wireless connection 3370 forms thelast segment.

A measurement procedure may be provided for the purpose of monitoringdata rate, latency and other factors on which the one or moreembodiments improve. There may further be an optional networkfunctionality for reconfiguring the OTT connection 3350 between the hostcomputer 3310 and UE 3330, in response to variations in the measurementresults. The measurement procedure and/or the network functionality forreconfiguring the OTT connection 3350 may be implemented in the software3311 of the host computer 3310 or in the software 3331 of the UE 3330,or both. In embodiments, sensors (not shown) may be deployed in or inassociation with communication devices through which the OTT connection3350 passes; the sensors may participate in the measurement procedure bysupplying values of the monitored quantities exemplified above, orsupplying values of other physical quantities from which software 3311,3331 may compute or estimate the monitored quantities. The reconfiguringof the OTT connection 3350 may include message format, retransmissionsettings, preferred routing etc.; the reconfiguring need not affect thebase station 3320, and it may be unknown or imperceptible to the basestation 3320. Such procedures and functionalities may be known andpracticed in the art. In certain embodiments, measurements may involveproprietary UE signaling facilitating the host computer's 3310measurements of throughput, propagation times, latency and the like. Themeasurements may be implemented in that the software 3311, 3331 causesmessages to be transmitted, in particular empty or ‘dummy’ messages,using the OTT connection 3350 while it monitors propagation times,errors etc.

FIG. 18 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station such as aAP STA, and a UE such as a Non-AP STA which may be those described withreference to FIGS. 16 and 17. For simplicity of the present disclosure,only drawing references to FIG. 18 will be included in this section. Ina first step 3410 of the method, the host computer provides user data.In an optional substep 3411 of the first step 3410, the host computerprovides the user data by executing a host application. In a second step3420, the host computer initiates a transmission carrying the user datato the UE. In an optional third step 3430, the base station transmits tothe UE the user data which was carried in the transmission that the hostcomputer initiated, in accordance with the teachings of the embodimentsdescribed throughout this disclosure. In an optional fourth step 3440,the UE executes a client application associated with the hostapplication executed by the host computer.

FIG. 19 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station such as aAP STA, and a UE such as a Non-AP STA which may be those described withreference to FIGS. 16 and 17. For simplicity of the present disclosure,only drawing references to FIG. 19 will be included in this section. Ina first step 3510 of the method, the host computer provides user data.In an optional substep (not shown) the host computer provides the userdata by executing a host application. In a second step 3520, the hostcomputer initiates a transmission carrying the user data to the UE. Thetransmission may pass via the base station, in accordance with theteachings of the embodiments described throughout this disclosure. In anoptional third step 3530, the UE receives the user data carried in thetransmission.

FIG. 20 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station such as aAP STA, and a UE such as a Non-AP STA which may be those described withreference to FIGS. 16 and 17. For simplicity of the present disclosure,only drawing references to FIG. 20 will be included in this section. Inan optional first step 3610 of the method, the UE receives input dataprovided by the host computer. Additionally or alternatively, in anoptional second step 3620, the UE provides user data. In an optionalsubstep 3621 of the second step 3620, the UE provides the user data byexecuting a client application. In a further optional substep 3611 ofthe first step 3610, the UE executes a client application which providesthe user data in reaction to the received input data provided by thehost computer. In providing the user data, the executed clientapplication may further consider user input received from the user.Regardless of the specific manner in which the user data was provided,the UE initiates, in an optional third substep 3630, transmission of theuser data to the host computer. In a fourth step 3640 of the method, thehost computer receives the user data transmitted from the UE, inaccordance with the teachings of the embodiments described throughoutthis disclosure.

FIG. 21 is a flowchart illustrating a method implemented in acommunication system, in accordance with one embodiment. Thecommunication system includes a host computer, a base station such as aAP STA, and a UE such as a Non-AP STA which may be those described withreference to FIGS. 16 and 17. For simplicity of the present disclosure,only drawing references to FIG. 21 will be included in this section. Inan optional first step 3710 of the method, in accordance with theteachings of the embodiments described throughout this disclosure, thebase station receives user data from the UE. In an optional second step3720, the base station initiates transmission of the received user datato the host computer. In a third step 3730, the host computer receivesthe user data carried in the transmission initiated by the base station.

Some example Embodiments numbered 1-9 are described below:

The following embodiments refer to FIG. 11, FIG. 12, FIG. 13, FIG. 14and FIG. 15.

Embodiment 1

A method performed by a User Equipment, UE, 120, e.g. for monitoring abeam transmitted by a base station 110 in a radio communications network100, which base station 110 is serving the UE 120, the method comprisingone or more out of:

monitoring 1202 a reference signal related to the beam, from the basestation 110,

each time a quality of the reference signal is below a first threshold,generating 1203 an Out-Of-Synchronization, OOS, event,

each time a quality of the reference signal is above a second threshold,generating 1204 an In-Synchronization, IS, event,

when the number of OOS events exceeds such as reaches an OOS BeamFailure Detection, BFD, threshold, and possibly the number of IS eventsis below an IS BFD threshold, triggering 1205 a beam recoverypreparation procedure,

when the number of OOS events reaches an OOS Radio Link Monitoring, RLM,threshold and possibly the number of IS events is below an IS RLMthreshold, declaring 1206 Radio Link Failure related to the beam,

wherein OOS RLM threshold and the OOS BFD threshold and possibly thewherein IS RLM threshold and the IS BFD threshold are configured suchthat the beam recovery preparation procedure is triggered beforedeclaring Radio Link Failure.

Embodiment 2

The method according to embodiment 1,

receiving 1201 from the base station 110 a configuration comprising atleast one reference signal related to the beam, which reference signalis to be monitored by the UE 120 for Beam Failure Detection, BFD, andcell-level Radio Link Monitoring, RLM,

Embodiment 3

A computer program comprising instructions, which when executed by aprocessor, cause the processor to perform actions according to any ofthe embodiment 1-2.

Embodiment 4

A carrier comprising the computer program of embodiment 3, wherein thecarrier is one of an electronic signal, an optical signal, anelectromagnetic signal, a magnetic signal, an electric signal, a radiosignal, a microwave signal, or a computer-readable storage medium.

Embodiment 5

A method performed by a Base station 110, e.g. for configuring a UE 120to monitor a beam transmitted the a base station 110 in a radiocommunications network 100, which base station 110 is serving the UE120, the method comprising configuring 1301 a UE 120 to one or more outof:

monitor a reference signal related to the beam, from the base station110, and

each time a quality of the reference signal is below a first threshold,generate an Out-Of-Synchronization, OOS, event,

each time a quality of the reference signal is above a second threshold,generate an In-Synchronization, IS, event,

when the number of OOS events reaches an OOS Beam Failure Detection,BFD, threshold, and possibly the number of IS events is below an IS BFDthreshold, trigger a beam recovery preparation procedure,

when the number of OOS events reaches an OOS Radio Link Monitoring, RLM,threshold and possibly the number of IS events is below an IS RLMthreshold, declare Radio Link Failure related to the beam,

wherein the OOS RLM threshold and the OOS BFD threshold and possiblyalso the IS RLM threshold and the IS BFD threshold, are configured suchthat the beam recovery preparation procedure is triggered beforedeclaring Radio Link Failure.

Embodiment 6

A computer program comprising instructions, which when executed by aprocessor, cause the processor to perform actions according to any ofthe embodiment 5.

Embodiment 7

A carrier comprising the computer program of embodiment 6, wherein thecarrier is one of an electronic signal, an optical signal, anelectromagnetic signal, a magnetic signal, an electric signal, a radiosignal, a microwave signal, or a computer-readable storage medium.

Embodiment 8

A User Equipment, UE, 120, e.g. for monitoring a beam transmitted by abase station 110 in a radio communications network 100, which basestation 110 is adapted to serve the UE 120, wherein the UE 120 isconfigured to one or more out of:

monitor a reference signal related to the beam, from the base station110, e.g. by means of a monitoring module 1410 in the UE 120, and

each time a quality of the reference signal is below a first threshold,generate an Out-Of-Synchronization, OOS, event, e.g. by means of agenerating module 1420 in the UE 120,

each time a quality of the reference signal is above a second threshold,generate an In-Synchronization, IS, event, e.g. by means of thegenerating module 1420 in the UE 120,

when the number of OOS events reaches an OOS Beam Failure Detection,BFD, threshold, and possibly the number of IS events is below an IS BFDthreshold, trigger a beam recovery preparation procedure, e.g. by meansof a triggering module 1430 in the UE 120,

when the number of OOS events reaches an OOS Radio Link Monitoring, RLM,threshold and possibly the number of IS events is below an IS RLMthreshold, declare Radio Link Failure related to the beam, e.g. by meansof a declaring module 1440 in the UE 120,

wherein the OOS RLM threshold and the OOS BFD threshold and possiblyalso the IS RLM threshold and the IS BFD threshold, are configured suchthat the beam recovery preparation procedure is triggered beforedeclaring Radio Link Failure.

Embodiment 9

The UE 120 according to embodiment 8, wherein the UE 120 is configuredto.

receive from the base station 110 a configuration comprising at leastone reference signal related to the beam, which reference signal is tobe monitored by the UE 120 for Beam Failure Detection, BFD, andcell-level Radio Link Monitoring, RLM, e.g. by means of a receivingmodule 1450 in the UE 120.

Embodiment 10

A Base station 110, e.g. for configuring a UE 120 to monitor a beamtransmitted the a base station 110 in a radio communications network100, which base station 110 is serving the UE 120, the base station 110being adapted to configure the UE 120, e.g. by means of a configuringmodule 1510 in the base station 110, to one or more out of:

monitor a reference signal related to the beam, from the base station110, and

each time a quality of the reference signal is below a first threshold,generate an Out-Of-Synchronization, OOS, event,

each time a quality of the reference signal is above a second threshold,generate an In-Synchronization, IS, event,

when the number of OOS events reaches an OOS Beam Failure Detection,BFD, threshold, and possibly the number of IS events is below an IS BFDthreshold, trigger a beam recovery preparation procedure,

when the number of OOS events reaches an OOS Radio Link Monitoring, RLM,threshold and possibly the number of IS events is below an IS RLMthreshold, declare Radio Link Failure related to the beam,

wherein the OOS RLM threshold and the OOS BFD threshold and possiblyalso the IS RLM threshold and the IS BFD threshold, are configured suchthat the beam recovery preparation procedure is triggered beforedeclaring Radio Link Failure.

Those skilled in the art will also appreciate that the modules in therespective base station 110 and UE 120, described above may refer to acombination of analog and digital circuits, and/or one or moreprocessors configured with software and/or firmware, e.g. stored in theUE 120 and/or the base station 110, that when executed by the respectiveone or more processors such as the processors described above. One ormore of these processors, as well as the other digital hardware, may beincluded in a single Application-Specific Integrated Circuitry ASIC), orseveral processors and various digital hardware may be distributed amongseveral separate components, whether individually packaged or assembledinto a system-on-a-chip SoC).

When using the word “comprise” or “comprising” it shall be interpretedas non-limiting, i.e. meaning “consist at least of”.

The embodiments herein are not limited to the above described preferredembodiments. Various alternatives, modifications and equivalents may beused.

The invention claimed is:
 1. A method performed by a User Equipment (UE)for monitoring a beam transmitted by a base station in a radiocommunications network, which base station is serving the UE, the methodcomprising: monitoring a reference signal related to the beam from thebase station; each time a quality of the reference signal is below afirst threshold, generating an Out-Of-Synchronization (OOS) event; whenthe number of OOS events reaches an OOS Beam Failure Detection (BFD)threshold, triggering a beam recovery preparation procedure; and whenthe number of OOS events reaches an OOS Radio Link Monitoring (RLM)threshold, starting an RLF timer, wherein the OOS BFD threshold and theOOS RLM threshold are distinct from each other.
 2. The method of claim1, further comprising: receiving from the base station a configurationcomprising at least one reference signal related to the beam, whichreference signal is to be monitored by the UE for BFD and cell-levelRLM.
 3. The method of claim 1, further comprising: each time a qualityof the reference signal is above a second threshold, generating anIn-Synchronization (IS) event.
 4. The method of claim 1, wherein:triggering the beam recovery preparation procedure is performed whenfurthermore, the number of IS events is below an IS BFD threshold. 5.The method of claim 4, wherein starting the RLF timer is performed when,furthermore, the number of IS events is below an IS RLM threshold. 6.The method of claim 5, wherein further: the IS RLM threshold and the ISBFD threshold are configured such that the beam recovery preparationprocedure is triggered before declaring Radio Link Failure.
 7. Themethod of claim 1, wherein starting the RLF timer further comprisesstarting to count IS events.
 8. The method of claim 7, furthercomprising if the RLF timer expires while the number of counted ISevents have not reached the IS RLM threshold, declaring Radio LinkFailure.
 9. The method of claim 8, further comprising if the number ofcounted IS events reaches the IS RLM threshold while the RLF timer isrunning, stopping the timer.
 10. The method of claim 1, wherein the OOSRLM threshold and the OOS BFD threshold are configured such that thebeam recovery preparation procedure is triggered before declaring RadioLink Failure.
 11. A method performed by a Base station, for configuringa UE to monitor a beam transmitted by the base station in a radiocommunications network, which base station is serving the UE, the methodcomprising configuring the UE to: monitor a reference signal related tothe beam from the base station, each time a quality of the referencesignal is below a first threshold, generate an Out-Of-Synchronization(OOS) event, when the number of OOS events reaches an OOS Beam FailureDetection (BFD) threshold, trigger a beam recovery preparationprocedure, when the number of OOS events reaches an OOS Radio LinkMonitoring (RLM) threshold, start an RLF timer, wherein the OOS BFDthreshold and the OOS RLM threshold are distinct from each other. 12.The method of claim 11, further comprising: configuring the UE to, eachtime a quality of the reference signal is above a second threshold,generate an In-Synchronization (IS) event.
 13. The method of claim 11,further comprising: configuring the UE to trigger the beam recoverypreparation procedure to be performed when furthermore, the number of ISevents is below an IS BFD threshold.
 14. The method of claim 13, furthercomprising: configuring the UE to start the RLF timer when furthermore,the number of IS events is below an IS RLM threshold.
 15. The method ofclaim 14, wherein configuring the UE to start the RLF timer furthercomprises starting to count IS events.
 16. The method of claim 15,further comprising configuring the UE to, if the RLF timer expires whilethe number of counted IS events have not reached the IS RLM threshold,declare Radio Link Failure.
 17. The method of claim 15, furthercomprising configuring the UE to, if the number of counted IS eventsreaches the IS RLM threshold while the RLF timer is running, stop thetimer.
 18. The method of claim 15, wherein: further, the IS RLMthreshold and the IS BFD threshold are configured such that the beamrecovery preparation procedure is triggered before declaring Radio LinkFailure.
 19. The method of claim 11, wherein: the OOS RLM threshold andthe OOS BFD are to be configured such that the beam recovery preparationprocedure is triggered before declaring Radio Link Failure.
 20. A UserEquipment (UE) for monitoring a beam transmitted by a base station in aradio communications network, which UE is adapted to be served by thebase station, the UE comprising: radio interface circuitry; andprocessing circuitry operatively coupled to the radio circuitry andconfigured to: monitor a reference signal related to the beam from thebase station, each time a quality of the reference signal is below afirst threshold, generate an Out-Of-Synchronization (OOS) event, whenthe number of OOS events reaches an OOS Beam Failure Detection (BFD)threshold, trigger a beam recovery preparation procedure, when thenumber of OOS events reaches an OOS Radio Link Monitoring (RLM)threshold, start an RLF timer, wherein the OOS BFD threshold and the OOSRLM threshold are distinct from each other.
 21. The UE of claim 20,wherein the processing circuitry is further configured to: receive fromthe base station a configuration comprising at least one referencesignal related to the beam, which reference signal is to be monitored bythe UE for BFD, and cell-level RLM.
 22. The UE of claim 20, wherein theprocessing circuitry is further configured to: each time a quality ofthe reference signal is above a second threshold, generate anIn-Synchronization (IS) event.
 23. The UE of claim 20, wherein theprocessing circuitry is further configured to: trigger the beam recoverypreparation procedure when, furthermore, the number of IS events isbelow an IS BFD threshold.
 24. The UE of claim 20, wherein theprocessing circuitry is further configured to start the RLF timer when,furthermore, the number of IS events is below an IS RLM threshold.
 25. Abase station, for configuring a UE to monitor a beam transmitted by thebase station in a radio communications network, which base station isadapted to serve the UE, the base station comprising: radio interfacecircuitry; and processing circuitry operatively coupled to the radiocircuitry and configured to use the radio interface circuitry toconfigure the UE to: monitor a reference signal related to the beam fromthe base station, each time a quality of the reference signal is below afirst threshold, generate an Out-Of-Synchronization (OOS) event, whenthe number of OOS events reaches an OOS Beam Failure Detection (BFD)threshold, trigger a beam recovery preparation procedure, when thenumber of OOS events reaches an OOS Radio Link Monitoring (RLM)threshold, start an RLF timer, wherein the OOS BFD threshold and the OOSRLM threshold are distinct from each other.
 26. A non-transitorycomputer-readable medium comprising, stored thereupon, computer programcode for execution by a processing circuit of a user equipment (UE), thecomputer program code being configured to, upon execution by theprocessing circuit, cause the UE to: monitor a reference signal relatedto a beam transmitted by a base station in a radio communicationsnetwork, the base station serving the UE, each time a quality of thereference signal is below a first threshold, generate anOut-Of-Synchronization (OOS) event, when the number of OOS eventsreaches an OOS Beam Failure Detection (BFD) threshold, trigger a beamrecovery preparation procedure, when the number of OOS events reaches anOOS Radio Link Monitoring (RLM) threshold, start an RLF timer, whereinthe OOS BFD threshold and the OOS RLM threshold are distinct from eachother.